postabdomen

Postabdomen is an anatomical term used in some arthropod groups to denote the posterior portion of the abdomen, behind the main body regions. In arachnology, its usage is most common in scorpions. Scorpions possess a two-part abdomen: the prosoma (cephalothorax) and the opisthosoma (abdomen). The opisthosoma is further divided into a preabdomen (mesosoma) and a postabdomen (metasoma). The postabdomen consists of several segments that form a tail-like region, ending in the telson, which carries the venom apparatus in most species. The postabdomen is often flexible and can be raised or curved during locomotion and prey capture; its segmentation and shape are important diagnostic traits in identification.

Outside scorpions, the term postabdomen is used in some crustaceans and other arthropods to describe the posterior portion of the abdomen behind the thoracic region. In these groups the exact boundaries and composition can vary; sometimes the postabdomen includes the final abdominal segments and associated structures such as uropods. In many taxonomic works, however, the term is not standardized and authors may use alternative terminology such as metasoma (in scorpions) or simply refer to the abdomen without subdividing it.

In summary, the postabdomen denotes the rear portion of the abdomen in certain arthropods, most notably scorpions, where it forms the tail-bearing segments of the body and ends with the venom-containing telson. The term’s precise meaning varies across taxa.